A Phytophthora effector suppresses trans-kingdom RNAi to promote disease susceptibility

Yingnan Hou, Yi Zhai, Li Feng, Hana Z. Karimi, Brian D. Rutter, Liping Zeng, Du Seok Choi, Bailong Zhang, Weifeng Gu, Xuemei Chen, Wenwu Ye, Roger W. Innes, Jixian Zhai, Wenbo Ma

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163 Citations (Scopus)


RNA silencing (RNAi) has a well-established role in anti-viral immunity in plants. The destructive eukaryotic pathogen Phytophthora encodes suppressors of RNAi (PSRs), which enhance plant susceptibility. However, the role of small RNAs in defense against eukaryotic pathogens is unclear. Here, we show that Phytophthora infection of Arabidopsis leads to increased production of a diverse pool of secondary small interfering RNAs (siRNAs). Instead of regulating endogenous plant genes, these siRNAs are found in extracellular vesicles and likely silence target genes in Phytophthora during natural infection. Introduction of a plant siRNA in Phytophthora leads to developmental deficiency and abolishes virulence, while Arabidopsis mutants defective in secondary siRNA biogenesis are hypersusceptible. Notably, Phytophthora effector PSR2 specifically inhibits secondary siRNA biogenesis in Arabidopsis and promotes infection. These findings uncover the role of siRNAs as antimicrobial agents against eukaryotic pathogens and highlight a defense/counter-defense arms race centered on trans-kingdom gene silencing between hosts and pathogens.
Original languageEnglish
Pages (from-to)153-165.e5
Number of pages19
JournalCell Host & Microbe
Issue number1
Early online date27 Dec 2018
Publication statusPublished - 9 Jan 2019

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